Precision or micro sieve structure

ABSTRACT

A precision micro sieve structure consists of a thin flexible metal sieve surface mounted between two annular bodies axially aligned with each other and connected together. An annular portion of the sieve surface contacts a bordering shoulder which is perpendicular to the axis of rotation of the annular bodies and is clamped therebetween while being made taut by an annular groove on one bordering shoulder and an annular land on the other bordering shoulder axially aligned with the annular groove. The opening of the groove is greater than the sum of the width of the land and twice the thickness of the sieve, while the depth of the groove is greater than the sum of the height of the land and the thickness of the sieve.

United States Patent 1191 Bolk [ June 10, 1975 PRECISION OR MICRO SIEVE STRUCTURE [75] Inventor: Fredrik Willem Bolk, Eerbeek,

[21] Appl. No.: 361,056

[30] Foreign Application Priority Data May 18, 1972 Netherlands 7206758 [56] References Cited UNITED STATES PATENTS 232,507 9/1880 Huntley et al. 209/403 622,217 4/1899 Fuller et all 210/445 1,138,741 5/1915 Fowler 209/403 X 2,042,106 5/1936 Knight 210/445 X 2,197,435 4/1940 Niemeyer 209/403 3,047,153 7/1962 Zelinski 209/403 X 3,286,338 11/1966 Bohr 209/403 X FOREIGN PATENTS OR APPLICATIONS 6,958 1/1914 United Kingdom 210/445 1,205,863 2/1960 France 210/445 327,209 10/1920 Germany 209/403 Primary ExaminerFrank W. Lutter Assistant Examiner-Ralph J. Hill Attorney, Agent, or FirmLittlepage, Quaintance, Murphy & Dobyns [57] ABSTRACT A precision micro sieve structure consists of a thin flexible metal sieve surface mounted between two annular bodies axially aligned with each other and connected together. An annular portion of the sieve surface contacts a bordering shoulder which is perpendicular to the axis of rotation of the annular bodies and is clamped therebetween while being made taut by an annular groove on one bordering shoulder and an annular land on the other bordering shoulder axially aligned with the annular groove. The opening of the groove is greater than the sum of the width of the land and twice the thickness of the sieve, while the depth of the groove is greater than the sum of the height of the land and the thickness of the sieve.

5 Claims, 3 Drawing Figures PRECISION OR MICRO SIEVE STRUCTURE BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a precision or micro sieve structure, having a frame comprising two annular bodies substantially in line with each other and mutually connected, and a flexible sieve surface mounted between bordering shoulders of said annular bodies.

2. Description of the Prior Art In known sieves of this type the sieve surface is typically soldered or clamped by screws or bolts onto a shoulder of a first annular body while a second annular body is arranged so as to contact the sieve surface with a clamping edge to keep the sieve surface in position. In this position the second annular body clampingly engages the first annular body and is internally soldered to the sieve surface. The annular bodies usually consist of brass.

By pollution and sometimes also by oxidation, corrosion and wear of the solder, the tare or netweight of these sieve structures changes during use, so that for each accurate determination of the quantity of material upon the sieve the sieve structure must be weighed before as well as after each use. Moreover after some period of use, the appearance of these sieve structures are impaired, the sieve structures are not sufficiently strong and are easily deformable. Assembling a sieve of this type much time and for very fine sieves the soldering was hardly possible without damage to the sieve surface.

Improvements in sieves of this type have been tried including applying annular bodies of electrolytically (anodically) oxidized aluminium, called eloxated aluminium, bonded together and to the sieve surface by use of an adhesive. Such sieves could rapidly be mounted, were cheap and had a more attractive appearance. However, in such structures the sieve surface often was not maintained taut but became slack by differences in expansion coefficients of the annular bodies and of the sieve surface, which often consisted of electrolytic nickel. Moreover, the adhesive connection between the several substances was not resistant to purgation by substances such as acetone, particularly at the higher temperatures necessary for drying (e.g. 105C).

SUMMARY OF THE INVENTION The invention aims at improving such sieve structures by forming annular bodies having bordering shoulders extending substantially parallel to the plane of the sieve surface, one of the shoulders having an annular raised part or land and the mating shoulder having an annular groove into which the raised part fits with sufficient clearance to permit an edge part of the sieve surface itself to be pressed by the raised part into the groove when moving the annular bodies towards each other tensioning the sieve surface to a flat plane. The raised part has a rounded end face. The groove at its opening is wider than the width of the raised part augmented by two times the thickness of the sieve surface and is deeper than the height of the land. This structural arrangement permits the shoulders to contact the sieve surface in the zone radially within groove and raised part in a clamping manner between them without permanently clamping the sieve surface between the land and groove in the area of the groove.

It is thereby easily possible to use thin annular bodies, e.g., from stainless steel or titanium, which can be connected mutually by flanging or swaging in a hermetically sealed manner. The sieve surface is tensioned by the land or raised part and groove without tearing or inadmissible deformation, e.g., due to stressing above the elastic limit. The sieve is not bent or bulged considerably and sharply but rather is allowed to slip somewhat along said raised part, the shoulders ensuring the clamping of the sieve surface immediately after the tensioning moreover no solder or adhesive is necessary and there is no space which can collect undesirable contaminating material. The sieve structure thus obtained is very good resistant against temperature shocks, the heat expansion coefficients of the parts are essentially the same and the sieve structure has a better chemical resistance.

Preferably the sieve structure according to the invention is embodied in such a way that at least part of one of the shoulders radially within the annular raised land or groove when in an unloaded condition, makes a small angle to the sieve surface. When assembling the sieve structure by moving the annular bodies towards each other, the shoulder will clamp onto the sieve surface tirst with its radial inner edge after the sieve surface has been tensioned by raised part and groove. The inclined shoulder part is provided on a part of one of the annular bodies which, in the axial direction, is relatively thin, so that this shoulder, when clamping the annular bodies onto each other with the sieve surface in between adapts itself to and becomes more parallel to the opposite shoulder.

The small angle is preferably about 4. A sieve structure having this feature effectively prevents contaminating material or sieved material from penetrating the space between the annular bodies. Moreover, this feature permits the sieve surface, in the area of the land and groove, to be better relieved from radial stresses.

The connection between the annular bodies is preferably according to the invention, obtained in such a way that one of the annular bodies has a groove in the outer periphery and the other body has a thin edge of an axially extending part. The thin edge is extended inwardly into said groove by having been swaged there into or by being adapted to be swaged there into in a later stage. The groove is positioned at an axial distance from the sieve surface such that, by widening the groove in the axial direction towards the sieve surface, an edge of an axially extending part of the other annular body may again be swaged into said groove after removing the former swaged edge e.g., on a lathe.

It is thus possible to repair a sieve by using the same set of annular bodies more than once.

Preferably, the peripheral portion of the sieve which is clamped between the annular bodies is non-porous and of the same thickness as the sieve surface itself but without sieve openings. It is, however, also possible to apply sieve surfaces which have sieve openings in their clamped edge parts, since the sieve surface is conventionally made by cutting it from a continuous perforated plate of larger size. In the latter case it is preferred to position a closed falt thin ring without sieve openings onto the peripheral part of the sieve surface,

so that everywhere where the sieve surface is clamped BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a part axial section to one side of the axis of a sieve structure according to a preferred embodiment of the invention in an intermediary position during assembly.

FIG. 2 is the same section in entirely assembled condition.

FIG. 3 is a section through part of a sieve with a closed ring in contact therewith for use in a sieve structure according to the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The sieve structure consists of three parts, two annular bodies 1 and 2 and a sieve surface 3 between them. Body 1 has a shoulder 4 perpendicular to the axis of the sieve structure and in said shoulder 4 there is an annular continuous raised part or land 5 rounded at its upper surface. Moreover this body 1 has a peripheral groove 6 in the outer periphery.

The body 2 has an axially protruding thin edge part 7 which engages fittingly around body 1 and which protrudes past the edge of groove 6 such that it may be swaged into said groove. Moreover, this body 2 has a shoulder part 8 perpendicular to the axis, a continuous groove 9 and a shoulder part 10 radially within said groove, which part 10 is conical and makes a very small angle of approximately 4 to the purely radial position, such that the inner edge 11 during assembly is closest to the shoulder 4 of body 1. The edge 11 is provided at the inwardly extending part 12 of said body which is rather thin, so that in clamping the sieve surface it is able to move away somewhat to bring the shoulder part 10 in a plane substantially perpendicular to the axis. The groove 9 in mounting is positioned opposite the raised part 5, so that the land is adapted to engage into said groove.

The sieve surface 3 is very thin and flexible and has, in the embodiment of FIGS. 1 and 2, a closed outer peripheral part, without sieve openings, radially outwardly of the circle indicated by 13.

In assembling the structure (FIG. 1) the sieve surface 3 is laid into the annular body 2 and body 1 is slid into body 2, the edge part 7 guiding these bodies mutually in the correct mutual position.

In the position shown in FIG. 1 the bodies 1 and 2 have approached each other so far that the sieve surface 3 is bent by the edges of groove 9 over the raised part 5, which tensions the sieve surface 3 to be exactly flat and tight. In the position of FIG. 1 the edge 11 has just enclosed the sieve surface 3 between itself and shoulder 4. When moving the annular bodies 1 and 2 further towards each other into the position of FIG. 2 the clamping force onto the sieve surface between edge 11 and the shoulder 4 increases since the groove 9 is substantially wider than the raised part 5, the sieve surface is not clamped tightly between parts 5 and 9, but is allowed to slip through the space between said parts 5 and 9 to be relieved from radial tensions. Meanwhile, part 12 of body 2 is bent upwardly until shoulder part 10 has taken up a position substantially or entirely perpendicular to the axis of the sieve structure and so it engages the sieve surface 3 over a wider radial area than only by its edge 11, thereby clamping the sieve surface and also obtaining a good seal between the annular parts.

The height of the raised part 5 is smaller than the depth of the groove 9. The width of said groove 9 in radial direction is greater than the radial width of the raised part 5 supplemented by two times the thickness of the sieve surface.

When the position of FIG. 2 is obtained, the end of the thin edge part 7 of body 2 is swaged into groove 6 whereby a tight and hermetically sealed connection is obtained without soldering and Without the risk of contamination. If it is desired to mount a new sieve surface 3, it is possible to cut away or to turn away on a lathe the swaged part of edge part 7, to turn the groove 6 to a somewhat wider groove in the axial direction towards the sieve surface 3 as shown by a dotted line 14 in FIG. 2, and to swage the edge part 7 which is now somewhat shorter again into said groove. It is possible to repeat this more than once if desired.

FIG. 3 shows a sieve surface 3 having sieve openings up to its outer edge 15 all over its surface. When used in combination with bodies 1 and 2, it is preferred to position a closed thin ring 16 into contact with sieve surface 3, which ring 16 has about the same small thickness as the sieve surface. Such a ring 16 may often be much thinner than one tenth of a millimeter. The ring preferably extends inwardly up to the edge 13 (FIGS. 1 and 2).

The bodies 1 and 2 make a mutual piling of such sieve structures onto one another possible, in which one structure is centered into the other, so that it is possible to use a cascade of sieves of different size of the openings, as is known as such.

I claim:

1. A precision micro structure comprising two annular bodies axially aligned with each other and connected together, a flexible sieve surface mounted therebetween, an annular portion of the sieve surface being in contact with a bordering shoulder on each of the annular bodies, each bordering shoulder being substantially perpendicular to the axis of rotation of the annular bodies, the improvement comprising an annular groove on one bordering shoulder, an annular land on the other bordering shoulder axially aligned with the annular groove and adapted to fit therein, the opening of the groove being greater than the sum of the width of the land and twice the thickness of the sieve, and the depth of the groove being greater than the sum of the height of the land and the thickness of the sieve, whereby the annular portion of the sieve surface is clamped between the bordering shoulders of the annular bodies except in the region of the land and groove.

2. A sieve structure according to claim 1 wherein the portion of one of said bordering shoulders radially within the annular land or groove is angularly displaced with respect to the sieve surface such that its radial inner edge will first contact the sieve surface and then deflect'into a position parallel to the other bordering shoulder.

3. A sieve structure according to claim 1 wherein a first of the annular bodies has a groove in the outer periphery of the body positioned axially remote from the bordering shoulder and the second of the annular bodies has a thin edge extending axially from its outer periphery coaxially over said first annular body and inwardly into said groove.

4. A sieve structure according to claim 1 wherein the peripheral portion of the sieve surface clamped between the bordering shoulders of the annular bodies is the peripheral portion of the sieve surface which is without sieve openings. clamped between the bordering shoulders of the annu- 5. A sieve structure according to claim 1 further lar bodies. comprising a thin, fiat ring positioned in contact with 

1. A precision micro structure comprising two annular bodies axially aligned with each other and connected together, a flexible sieve surface mounted therebetween, an annular portion of the sieve surface being in contact with a bordering shoulder on each of the annular bodies, each bordering shoulder being substantially perpendicular to the axis of rotation of the annular bodies, the improvement comprising an annular groove on one bordering shoulder, an annular land on the other bordering shoulder axially aligned with the annular groove and adapted to fit therein, the opening of the groove being greater than the sum of the width of the land and twice the thickness of the sieve, and the depth of the groove being greater than the sum of the height of the land and the thickness of the sieve, whereby the annular portion of the sieve surface is clamped between the bordering shoulders of the annular bodies except in the region of the land and groove.
 2. A sieve structure according to claim 1 wherein the portion of one of said bordering shoulders radially within the annular land or groove is angularly displaced with respect to the sieve surface such that its radial inner edge will first contact the sieve surface and then deflect into a position parallel to the other bordering shoulder.
 3. A sieve structure according to claim 1 wherein a first of the annular bodies has a groove in the outer periphery of the body positioned axially remote from the bordering shoulder and the second of the annular bodies has a thin edge extending axially from its outer periphery coaxially over said first annular body and inwardly into said groove.
 4. A sieve structure according to claim 1 wherein the peripheral portion of the sieve surface clamped between the bordering shoulders of the annular bodies is without sieve openings.
 5. A sieve structure according to claim 1 further comprising a thin, flat ring positioned in contact with the peripheral portion of the sieve surface which is clamped between the bordering shoulders of the annular bodies. 